Optimized accelerator-extractor pairs for fluid power generation

ABSTRACT

A device includes an extractor structurally configured to extract energy from a fluid flow, an accelerator structurally configured to accelerate a fluid stream through the extractor thereby creating an accelerated fluid stream, and an extractor feature structurally configured to minimize blockage of the accelerated fluid stream. The extractor feature may include one or more of a linear cascade, an oscillating foil, and an axial extractor.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional App. No. 62/149,821 filed on Apr. 20, 2015, the entire content of which is hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under contract W911QY-13-C-0054 awarded by the Department of Defense. The government has certain rights in the invention.

TECHNICAL FIELD

The present disclosure generally relates to devices, systems, and methods for maximizing power output from accelerator-extractor pairs in fluid flows.

BACKGROUND

The power performance of fluid accelerator-extractor systems is generally determined by the rate of blockage experienced by the accelerator due to the extractor. This rate of blockage is generally a combination of a given rate of power extraction (power blockage) and the specific flow field engendered by extracting power (non-power blockage) with a given extractor. In free stream turbines the axial induction (a) (a way of characterizing blockage relative to the swept area or max area of a given device) and the power coefficient are similar until the higher power coefficients at which point axial induction is less than the power coefficient. The axial induction factor can be defined as the fractional decrease in wind velocity between the free stream and an energy extraction device, generally in the form:

$a = \frac{v_{1} - v_{2}}{v_{1}}$

The relationship between the axial induction and the power coefficient can be depicted in a classic Betz graph comparing P/P_(o) to v₂/v₁.

Once an extractor is placed in an accelerator, however, this relationship may no longer be based purely on the extractor, but on the power extraction of the extractor and the extractor's interaction with the accelerator. Therefore, the axial induction and power coefficient may vary based on the interaction of a particular accelerator-extractor pair. If blockage is high, the axial induction can be significantly higher than the power extraction coefficient related to the maximum area of the accelerator (e.g., the maximum area comparison determines whether the accelerator is providing any benefit to power production compared to the same swept area free stream device) which has led to erroneous conclusions about accelerators in the prior art. If the blockage is above the critical point, where benefits can be derived from accelerators, then the axial induction is higher than the power coefficient (Cp). If blockage is reduced solely to the blockage engendered by the power extraction, then the Cp can be a multiple of the axial induction experienced by the device. For example, an accelerator with a 2× area ratio (AR) with no non-power blockage can have power coefficients that are six times the axial induction of the device. Due to power blockage this Cp:a ratio reduces as the Cp increases to the theoretical maximum.

In general, to date, no accelerator-extractor pair has yielded a Cp that is significantly higher than the axial induction (a) of the device. This is primarily due to the pairs that have been examined in the field for the last 30 years or so. Prior implementations are generally limited to pairing wide angle (e.g., 20-40 degrees) diffuser augmented wind turbines (DAWTs) with axial rotary extractors of between two and eight blades (horizontal axis wind turbines (HAWTs), wind, or HATs, water). In addition to DAWTs being inefficient accelerators (if the baseline acceleration in an empty accelerator is too low relative to the AR, the device will not achieve the critical point) HAWT/HATs engender highly non-uniform flow with significant flow and momentum effects to the outside of the device and therefore significant blockage and high value of a when placed in accelerators. A further complication is that improving the DAWT's accelerative capabilities by reducing the expansion angle may increase interaction between the HAWT/HAT's tip vortex wake spiral and the diffuser wall which dissipates the wake's transport energy thereby stalling the wake in the diffuser which through mass conservation engenders a reduction in intake velocity and an increase in the value of a. Any interaction of the extractor flow field with the walls of the accelerator anywhere in the accelerator may induce blockage at the intake due to the reduction in available transport energy and the communication of such losses through the accelerator volume to the velocity at the intake.

Due to this state of affairs it remains desirable to move beyond the prior art and pair accelerators with extractor devices that reduce the interaction between the pair, or to introduce mechanisms on accelerators by which the effect of any interaction can be counterbalanced (or both).

SUMMARY

A device includes an extractor structurally configured to extract energy from a fluid flow, an accelerator structurally configured to accelerate a fluid stream through the extractor thereby creating an accelerated fluid stream, and an extractor feature structurally configured to minimize blockage of the accelerated fluid stream. The extractor feature may include one or more of a linear cascade, an oscillating foil, and an axial extractor.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the devices, systems, and methods described herein will be apparent from the following description of particular embodiments thereof, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the devices, systems, and methods described herein.

FIG. 1 shows a reversible camber oscillating airfoil with a uniform guide path.

FIG. 2 shows a reversible camber oscillating airfoil with a variable guide path.

FIG. 3 shows a reversible camber airfoil.

FIG. 4 shows a reversible camber airfoil.

FIG. 5 shows a linear array of oscillating airfoils.

FIG. 6 shows an array of oscillating airfoils.

FIG. 7 shows an array of oscillating airfoils.

FIG. 8 shows an array of oscillating airfoils.

FIG. 9 shows a spiraling geometry.

FIG. 10 shows a spiraling geometry.

FIG. 11 shows a device cycle for an axial extraction parafoil.

FIG. 12 shows a PIV example of wall proximity blockage in a Savonius turbine.

FIG. 13 illustrates effects of wall interaction with wake energy.

FIG. 14 shows an effect of a non-uniform wake on a nozzle function.

FIG. 15 depicts a two-dimensional linear modular array.

FIG. 16 shows single and double stage tilted linear cascades.

FIG. 17 shows a CD nozzle with variable expansion and vanes.

FIG. 18 shows a CD nozzle with variable expansion and vanes.

FIG. 19 shows triangular circuit linear cascades.

FIG. 20 shows triangular circuit linear cascades.

FIG. 21 shows trends in nozzle performance with linear cascades.

FIG. 22 shows simulation results for an energy extractor.

FIG. 23 shows simulation results for a two stage energy extractor.

FIG. 24 shows a graph illustrating the degree of blockage.

FIG. 25 shows a device for fluid power generation.

FIG. 26 shows a device for fluid power generation.

DETAILED DESCRIPTION

The embodiments will now be described more fully hereinafter with reference to the accompanying figures, in which preferred embodiments are shown. The foregoing may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein. Rather, these illustrated embodiments are provided so that this disclosure will convey the scope to those skilled in the art.

All documents mentioned herein are incorporated by reference in their entirety. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the context. Grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context. Thus, the term “or” should generally be understood to mean “and/or” and so forth.

Recitation of ranges of values herein are not intended to be limiting, referring instead individually to any and all values falling within the range, unless otherwise indicated herein, and each separate value within such a range is incorporated into the specification as if it were individually recited herein. The words “about,” “approximately,” or the like, when accompanying a numerical value, are to be construed as indicating a deviation as would be appreciated by one of ordinary skill in the art to operate satisfactorily for an intended purpose. Ranges of values and/or numeric values are provided herein as examples only, and do not constitute a limitation on the scope of the described embodiments. The use of any and all examples, or exemplary language (“e.g.,” “such as,” or the like) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the embodiments or the claims. No language in the specification should be construed as indicating any unclaimed element as essential to the practice of the embodiments.

In the following description, it is understood that terms such as “first,” “second,” “top,” “bottom,” “up,” “down,” and the like, are words of convenience and are not to be construed as limiting terms unless specifically stated to the contrary.

Described herein are devices, systems, and methods for maximizing power output from accelerator-extractor pairs in fluid flows. In general, a variety of linear extractors and other non-rotary configurations for extracting power from a fluid flow are disclosed. While the emphasis is on arrangements suitable for extracting wind power from air flow, it should be understood that the principles of this disclosure may be suitably adapted to other fluid flows such as water or the like, as well as extractors used without accelerators, restrictors, or the like.

As used herein, “non-power blockage” generally refers to the difference between total blockage and a power blockage that has been theoretically and/or experimentally isolated, unless explicitly stated to the contrary or otherwise clear from the context.

U.S. Pat. Pub. No. 2013/0334824 to Freda (hereinafter “Freda”) describes various geometric optimizations, modular extractor configurations, and so forth. While the following description may focus on non-rotary extractor configurations, many aspects of Freda remain relevant to arrays of extractors using the principles described herein. As such, U.S. Pub. No. 2013/0334824 is hereby incorporated by reference in its entirety.

For example, in Freda, in general, geometric optimization parameters for high efficiency (e.g., >90%) accelerators are described. The diffusion angle on these accelerators may be between 8 and 2 degrees dependent on the AR of the given accelerator. These accelerator parameters may be included herein as the geometric optimization parameters for accelerators. Variance of these parameters outside the optimum range of performance may reduce the rate of acceleration and thereby available power. These parameters may not be varied to accommodate the wake and overall flow field of extractor devices without affecting the accelerative performance until, as in the case DAWTs, the accelerative performance is reduced to such a level that there is no benefit from the accelerator.

Therefore the accelerator parameters may be largely fixed to the previously described optimum geometries. Therefore, features that improve performance of accelerator-extractor pairs may be extractors that reduce flow field effects to the outside of the extractor area and/or features introduced to the accelerator geometry that may counteract the effects of the extractor.

As another example, in Freda various modular accelerator array systems are generally described where the benefits from such modular systems may be accrued to more efficient extractor-accelerator pairs. The accelerator-extractor pairs may include a modification of the systems described herein or may adhere to parameters of the described systems. Any accelerator-extractor pairs described herein may be applied if geometrically feasible to either the prior or modified modular systems.

In an implementation, a class of extractor systems that may be paired effectively with accelerators is axial rotary devices wherein the axial rotary devices may have about 3-128 blades, may be of variable average chord width globally or locally, may be n-staged counter-rotating or co-rotating, may vary blade number between stages, may vary pitch globally or locally from about 75 degrees to about negative 5 degrees, may have blades pitched at different average angles, may have global or local anhedral tilt, may have global or local sweep, may be single or multi-element airfoils or a combination thereof on single airfoil or single rotor or a combination thereof, may be spiraled in n-helix or n-helix segmented configurations, may include a stator or multiple stators, may have a combination of propeller and rotor behavior, may be n-staged propeller-rotor or rotor-propeller pairs, may vary in radius, position, and type between rotor or rotor-propeller or propeller-rotor stages, may be surfaced with aerodynamic enhancement features (e.g., as described in Freda), may have a cylindrical or n-polygonal tube hubs, may have hubs that extend to about 50% of rotor radius, may be uniformly or non-uniformly geared to generators exterior to the accelerator, may be attached to generator(s) with modularly engaged groups or windings, may be n-parafoil types, may have orthogonally and/or angled louvered blades, may include pressure release channels, may have variable chord dimensions outward and inward and orthogonally globally or locally and uniformly and non-uniformly, may have shaped tips such as u-tips or saw-edge tips or similar, and the like and may have any combination of the above features.

In an implementation, a class of extractor systems that may be paired effectively with these accelerators is radial rotary devices where the definition of rotary may include without limitation circular, elliptical, stadium, and linear paths and all closed geometric variations therein, may have paths that are oriented axially or radially internal or external to the accelerator, may include mechanisms to control pitch relative to axial flow locally or globally in a prescribed or adaptive manner, may have bearing and the like paths, may have mag-lev paths, may have invertible camber airfoils, may have about 3-200 blades, may be of variable average chord width globally or locally, may be n-staged counter-rotating or co-rotating (e.g., that draw power from an internal volume rather than a single plane), may vary blade number between stages, may vary pitch globally or locally from about 75 degrees to about negative 5 degrees, may have blades pitched at different angles, may have global or local anhedral tilt, may have global or local sweep, may be single or multi-element airfoils or a combination thereof on single airfoil or single device or a combination thereof, may be spiraled or tilted in n-helix or n-helix segmented configurations either axially or radially, may have a combination of propeller and rotor behavior, may include a stator, may be n-staged propeller-rotor or rotor-propeller pairs, may vary in radius, position, and type between rotor or rotor-propeller or propeller-rotor stages, may be surfaced with aerodynamic enhancement features (e.g., as described in Freda), may be uniformly or non-uniformly geared to generators exterior to the accelerator, may be attached to generator(s) with modularly engaged groups or windings, may be n-parafoil types, may have orthogonally and/or angled louvered blades, may include pressure release channels, may have variable chord dimensions vertically and orthogonally globally or locally and uniformly and non-uniformly, may have shaped tips such as u-tips or saw-edge tips or similar, and the like and may have any combination of the above features. Radial types may also be deployed within nozzles in n-device arrays wherein the arrays may be n-staged uniformly or non-uniformly in parallel or offset and may include tandem types such as tandem arrangements of 2, 3, 4, . . . n oscillating foils and the like, or may have any combination of the above features.

In an implementation, a class of extractor systems that may be paired effectively with these accelerators is axial motion extractors where axial motion extractors may include any device that extracts power through an oscillatory or non-oscillatory motion in parallel to the flow and the like. This may include electrostatic types, which may include ionic types or magnetic particulate types and the like, or harmonic extractors, vibrational or sinusoidal, or piston type extractors and the like. In an embodiment, an axial oscillatory device may include flow resistive aerodynamic shape such as a parafoil or airfoil or flat plate or symmetrically angled flat plate and the like oriented orthogonally or angled to the flow attached to a spring. The piston circuit may be circular, elliptical, stadium, or linear, or may be freeform as in the case of combination of tether types with magnetic particulates. “Spring” or the like may be used generally herein to describe any mechanism such as a spring or tether or other means of recovery such as magnetic that can return the foil with the energy stored in the mechanism. The foils may be of any scale within the volume or may cover the volume vertically or horizontally. The foil may have a cycle where the flow pushes the foil downstream against the generator loading and spring resistance and is returned by the recovery mechanism. The recovery mechanism may store the energy enabling the system to extract power on the recovery cycle. A foil device may include a collapsible foil where the foil may have a hinge such as a pinned metal or pressed hinge or the like down the centerline that may allow it to assume a flat or airfoil shape on the recovery cycle which may limit losses. The down flow and recovery cycle may be attached to a mechanism such as a gear or a linkage crank to produce rotation in a generator shaft or the path may be executed with a linear generator or the like to generate power on both the down and recovery cycles and the like and may have any combination of the above features. Axial motion extractors may also be deployed within nozzles in n-device arrays where the arrays may be n-staged uniformly or non-uniformly in parallel or offset and the like.

An embodiment may also include uniform or non-uniform spacing or tip gaps between the extractor and accelerator.

In an implementation, accelerator features that may reduce or counteract blockage due to an extractor may include forward or backward pitched elements on the outer or inner surface of the accelerator such as the exit or entrance or throat and may include linear or curved geometries such as a dimensionalized gurney flap or the like applied to the three-dimensional accelerator geometry or which may be positioned singly or in arrays and the like in combination with previously described optimal accelerator geometries, the forward or backward pitched elements as described that may be uniform or non-uniform or variable solidity and have porosity or edge features such as vortex generation geometries or scalloping or corrugation or the like and any combination thereof, may have variable thickness and curvature, may include pressure release mechanisms such as drill-throughs or open areas in the extractor region and the like or any combination thereof, may include flow control mechanisms internal or external anywhere along the length of the accelerator to control either the entrained flow or the external flow such as a saw edge intake and the like, may include active boundary layer mechanisms locally or globally applied as are known in the art such a plasma or injection control, may include passive mechanisms locally or globally applied as are known in the art such as scalloping or surface dimpling, may include any combination of passive and active flow control applied either locally or globally, and the like as are known in the art and may have any combination of the above features and features included by reference in the aforementioned patents and patent applications. The accelerators may be two-dimensional or three-dimensional accelerators with variable thickness inside and outside, they may have different curvature outside or inside, they may be deployed singly or in an array. The elements pitched forward or backward can be placed anywhere on the accelerator geometry and may range in geometry from a flat plate, to concave or convex on either side, where thickness and element shape can vary across the element.

All accelerator extractor pairs described herein may be deployed in two-dimensional or three-dimensional arrays. Adjustment of the vertical to horizontal aspect ratio may allow granular control of the value of power density per m̂2 horizontal surface. When blockage is resolved at a sufficient rate the power density of the modular arrays at a 2:1 aspect ratio may equal the power density of coal and is 30% of the power density of natural gas.

By way of specific examples:

a) high rpm (>500) three bladed horizontal rotors or H-type darrius vertical, 4 N thrust free stream, 90% blockage and ˜15% Cp.

b) linear cascades at low rpm (˜100), 4 N thrust free stream, 35% blockage and ˜55% Cp.

c) 25% Screen, 4 N thrust free stream, 15% blockage and the pressure drop across the screen indicates a ˜140% Cp.

An example is shown, e.g., in FIG. 22, where a 2.25 AR nozzle (including flap) is producing 66 watts, axial induction 0.33, and a Cp of 0.56. Thrust model for a 2.25 with a baseline acceleration of 1.75 yields 66 watts, 0.3 axial induction, and Cp of 0.56. Both throat velocities are ˜6.5 for free stream of 4.5. Two stage linear cascades in the free stream produce an axial induction of 0.12 for a Cp of 0.2. They maintain roughly this a:Cp ratio in accelerators.

The cascade also gives an example of a device that does not have three-dimensional uniform rotational effects across the device. The asymmetric effects make it easier to see the structure and its effect within the accelerator; see, e.g., FIG. 22, which shows a single row showing the asymmetric flow in the free stream and accelerator. The single rows are more efficient until the cascade effects take over at certain RPMs or AR ratios. Once the device flow effects dominate the function and expansion of the accelerator the efficiency may drop rapidly.

FIG. 24 shows the effect of AR on Cp when sufficient blockage has been resolved, as in the linear cascades.

If the total blockage (the pair's axial induction) is around or greater than the Cp then AR increase results in lower Cp's. If blockage is less than Cp due to a reduction in the extractor interaction then the Cp increases with AR until the accelerator geometries become problematic. The slope of the Cp to AR (the line in FIG. 24) reflects the degree of blockage in the pair engendered by the extractor.

This trend is predicted by the tube/accelerator thrust model as the requisite mass flow coefficient required to reach the minimum benchmark is lower as AR increases. These results are not optimized as extractor parameters are held stable, 60 degree pitch, 2 stages, counter-rotating, blade number of 12. The value 0.20 at 1 is the free stream rotor specific performance. In this graph, the AR includes the flap. The FIG. 23 graph is of best case at each AR. Solidity increase of 2 rows and/or the AR increase does not yield a corollary increase in overall axial induction as previously predicted in the art. A variety of linear or other non-rotary extractors may be usefully devised to extract wind power without the use of turbines.

FIG. 1 shows a reversible camber oscillating airfoil with a uniform guide path. The system, which is generally shown in multiple views in the figure (a first view 100, a second view 101, and a third view 103), may, for example, use non-flexible arc foils 102 such as NACA 9501 or the like (the foils 102 may also be referred to herein as airfoils). As illustrated, the foil 102 may be secured to an endplate 104 (or multiple endplates 104, e.g., on opposing ends), and have an oscillating motion cycle 106 that rotates about bearing blocks 108 (e.g., linear bearing blocks) or the like between two positions defined by mechanical stops such as pitch restraint pegs 110 or the like. A turning peg 111 may act on the endplate 108 from a top of the foil 102 to support an oscillating motion cycle 106.

FIG. 2 shows a reversible camber oscillating airfoil with a variable guide path. Specifically, this figure shows three positions (a first position 200, a second position 201, and a third position 203 of a foil 202). In this embodiment, a turning peg 211 may act on the endplate 204 at a bottom of the foil 202 as generally illustrated to support an oscillating motion cycle 206. The figure also shows the bearing block 208 (e.g., linear bearing block) and pitch restraint pegs 210.

FIG. 3 shows a reversible camber airfoil. In this system 300, the foil 302 may be a flexible foil, with foil parameters controlled with rigid LE and TE elements 312 in combination with the elastic modulus of the flexible foil section 314. The turning peg 311 and pitch restraint peg 310 may act on the endplate(s) 304 to support an oscillating motion cycle 306 on linear bearing blocks 308.

FIG. 4 shows a reversible camber airfoil. In general, an entry cycle 400 and an exit cycle 401 may be fixed by wind, with an intervening turning cycle 403 generating rotational motion. The foil may be flipped thereby providing a flipped foil 405 as shown in the figure.

FIG. 5 shows a linear array of oscillating airfoils. A foil array 500 can be used with either a camber system or flat plates, and may include a number of foils 502 in a line or other linear or non-linear arrangement. These foils 502 may also be mechanically coupled to one another (e.g., via an array endplate 514), or these foils 502 may be independently operable. The figure further shows the foil endplates 504, foil endplate couplers 505, a bearing block 508 (e.g., a linear bearing block), a pitch restraint peg 510, and a turning peg 511 that acts on the endplate 504 of the foil 502.

FIG. 6 shows an array of oscillating airfoils. As illustrated, these oscillating foils 602 may be placed in the throat 616 of a restrictor, nozzle, or the like to increase air flow about the foils, and the airfoils may oscillate in tandem either through mechanical coupling or aerodynamic coupling.

FIG. 7 shows an array of oscillating airfoils. As illustrated, any number of tandem airfoils 602 may be used, such as two airfoils, four airfoils, six airfoils, and so forth. The airfoils may be disposed in the throat 716 of a restrictor, nozzle, or the like to increase air flow.

FIG. 8 shows an array of oscillating airfoils. In particular, eight tandem oscillating airfoils 802 are depicted in the throat 816 of a restrictor, nozzle, or the like.

FIG. 9 shows a spiraling geometry. In particular, in a first spiraling geometry 900, a nozzle 920 is depicted with a zero offset between foils 902 as shown by the first line 922. As shown in the first spiraling geometry 900 of the figure, the axial LE to LE may be the same for the foils 902. In a second spiraling geometry 902, the nozzle 920 or tube is depicted with a ten degree offset (relative to a direction of fluid flow) between two sequential airfoils as shown by the second line 924 offset from the first line 922. As shown in the second spiraling geometry 902 of the figure, the axial LE to LE may be the same for the foils.

FIG. 10 shows a spiraling geometry. In particular, the figure shows a first view 1000 illustrating a full isometric view of the geometry and a second view 1001 showing a variety of segmented views of the geometry.

FIG. 11 shows a device cycle for an axial extraction parafoil. As depicted, the parafoil may open and close on a hinge 1102 or the like to provide cycles of linear displacement, e.g., against a spring, coil or the like, and relaxation. Thus, the foil may open at a hinge as shown in step 1, and may be drawn linearly in a direction of fluid flow. This linear motion may be converted on a spool or the like into a rotational motion to drive a generator. In the return cycle (step 3), the foil may return to an initial position, e.g., through a spring or the like on the spool, or otherwise using a portion of the power extracted during the out cycle (step 2). Once the foil has returned to the starting position (step 4), the process may return to step 1 and the hinge may be open to once again capture force from an incident fluid flow.

FIG. 12 shows a PIV example of wall proximity blockage in a Savonius turbine. In particular, a first top view 1200 of a vertical axis wind turbine blade is shown in a 25% open channel, and a second top view 1201 of a vertical axis wind turbine blade is shown in a free stream without adjacent walls. As shown in this figure, substantial blockage may be evident around the tips of the turbine blade that are adjacent to the wall even with 25% of linear open space around the blade tips.

Thus, as demonstrated by FIG. 12, use of vertical extraction devices, e.g., vertical axis turbines may be used in the devices, systems, and methods described herein. For example, this may include Savonius turbines or the like, or otherwise vertically mounted airfoils.

The devices, systems, and methods described herein may also or instead include two or more sequential rotors on a common axis. For example, the common axis may be a horizontal axis, thereby creating a horizontal extraction device. In another aspect, the common axis may be a vertical axis. In certain aspects, sequential rotors may rotate in the opposite direction of one another, thereby creating a multi-stage extraction device, e.g., a multi-stage horizontal extraction device. For example, one aspect includes a two stage assembly, where the second stage rotates in the opposite direction of the first stage. Considerations for the design of such assemblies include without limitation power extraction performance, cost, manufacturability, reliability, maintenance requirements, and so forth.

In multiple rotor assemblies as described herein, multiple sets of rotor blades may be disposed on the same shaft (such as in a steam turbine), or multiple sets of rotor blades may be disposed on multiple shafts, e.g., multiple horizontal shafts.

FIG. 13 illustrates effects of wall interaction with wake energy. In general, blockage may be caused by the wall interaction with wake energy caused by the turbine, e.g., at the tips of the turbine blades. The interaction may be affected by anhedral tilt. The figure shows a first image 1300 illustrating an anhedral tilt rotor at forty degrees and a second image 1302 illustrating an anhedral tilt rotor at twenty degrees 1310. At forty degrees, the blockage may be equal to 0.55 with a Cp=0.31 intake; at twenty degrees, the blockage may be equal to 0.65 with a Cp=0.2 intake. Diffuser acceleration and interaction may include, for example, a low interaction and a high interaction. An example of a low interaction may include a relatively short diffuser with a 1.3× baseline and a Cp=0.54 exit. An example of a higher interaction may include a relatively long diffuser with a 1.8× baseline and a Cp=0.31 exit.

FIG. 14 shows an effect of a non-uniform wake on a nozzle function. In particular, a first accelerator 1400 and a second accelerator 1402 are shown. The first accelerator 1400 may include a rotor with a relatively low velocity through the constriction. The second accelerator 1402 may include a relatively high velocity through the same constriction as the first accelerator 1400, where the rotor of the second accelerator 1402 is replaced by a radial screen of equal area. The first accelerator 1400 may include a cross-section rotor in a 2.75 area ratio accelerator, where the freestream thrust is 4.5 N, the thrust blockage is 0.25, and the blockage is 0.63. The second accelerator 1402 may include a cross-section radial screen in a 2.75 area ratio accelerator, where the freestream thrust is 3.7 N, the thrust blockage is 0.21, and the blockage is 0.27.

FIG. 15 depicts a two-dimensional linear modular array. Specifically, the figure shows a linear modular array 1500 and a velocity profile 1502 through the array.

FIG. 16 shows single and double stage tilted linear cascades. Specifically, the figure shows two models, a first model 1600 showing a single stage tilted linear cascade, and a second model 1602 showing a double stage tilted linear cascade.

FIG. 17 shows a converging/diverging (CD) nozzle 1700 with variable expansion and vanes 1702.

FIG. 18 shows a CD nozzle with variable expansion and vanes. The nozzle 1800 may include vanes 1802 offset at about 6 degrees from a longitudinal axis 1804 through the nozzle 1800.

FIG. 19 shows triangular circuit linear cascades. Specifically, the figure shows a first cascade 1900 and a second cascade 1902. The first cascade 1900 may include a triangular circuit linear cascade in the general shape of an asymmetric isosceles (20:12 degree). The second cascade 1902 may include a triangular circuit linear cascade in the general shape of an asymmetric isosceles (20:−15 degree).

FIG. 20 shows triangular circuit linear cascades. Specifically, the figure shows a first cascade 2000 and a second cascade 2002. The first cascade 2000 may include a triangular circuit linear cascade in the general shape of an asymmetric isosceles (20:12 degree, tube arrangement). The second cascade 2002 may include a triangular circuit linear cascade in the general shape of an asymmetric isosceles (30:−15 degree, nozzle offset arrangement).

FIG. 21 shows trends in nozzle performance with linear cascades. Specifically, the figure shows a graph 2100 and a table 2102 showing trends and examples of nozzle performance with linear cascades. The bars on the graph 2100 represent the power coefficient (max area power) and the points (*) connected by lines represent axial induction. The table 2102 shows, for example case numbers, each of the stage, row tilt, and AR.

FIG. 22 shows simulation results for an energy extractor. Specifically, the figure shows a first model 2200, a second model 2210, a first set of data 2202 for an example case, and a second set of data 2212 for an example case. For the first model 2200, the maximum theoretical at Cp=0.3 may be 121 watts, where a=0.21, vmax is 7.12, and thrust is 17.3 N. Performance on cylinders at Cp˜0.5. thrust thus appears to overestimate. For the second model 2210, the structure may match that of PIV of louver flow (not rotational).

FIG. 23 shows simulation results for a two stage energy extractor. Specifically, the figure shows a first model 2300, a second model 2310, a first set of data 2302 for an example case, and a second set of data 2312 for an example case. For the first model 2300, there may be similar axial induction for greater than two times the solidity in a two-stage linear cascade. This may include an ‘a’ ratio of 1.13 and a solidity ratio of 2.2. As shown in the second model 2310, counter-rotating appears to make the flow more symmetrical. Thus, the one-stage may be split into two with the same blade count.

FIG. 24 shows a graph illustrating the degree of blockage. Specifically, the graph 2400 shows an example of the effect of AR (shown on the x-axis 2402) on Cp (shown on the y-axis 2404) when sufficient blockage has been resolved, e.g., as in the linear cascades. If the total blockage is around or greater than the Cp then AR increase may result in lower Cp's. If the blockage is less than Cp (e.g., due to a reduction in the extractor interaction) then the Cp may increase with AR until the accelerator geometries become problematic. The slope of the Cp to AR (the line 2406) may reflect the degree of blockage in the pair engendered by the extractor.

FIG. 25 shows a device for fluid power generation. As shown in the figure, the device 2500 may include an extractor 2502, an accelerator 2504, and an extractor feature 2506 that may provide for optimized fluid power generation for the device 2500.

The figure also shows a first fluid flow 2508 into the device 2500 (v_(∞)) and a second fluid flow 2510 out of the device 2500 (v_(wake)). The figure further shows a first area bounded by a first dashed line 2512 that represents a maximum area reference plane of the outer streamtube, and a second area bounded by a second dashed line 2514 that represents a disk area reference plane of the inner streamtube.

The extractor 2502 may include any as described herein or otherwise known in the art, e.g., a turbine, a rotor, a fan, and the like. In general, the extractor 2502 may be structurally configured to extract energy from a fluid flow. The fluid flow may be any as described herein or otherwise known in the art, e.g., air (e.g., wind), water, gas, exhaust, and the like.

The accelerator 2504 may include any as described herein or otherwise known in the art. For example, the accelerator 2504 may include a structure that confines the flow of the fluid being extracted, e.g., a nozzle, a diffuser, a cavity, a chamber, a channel, a tube, or the like. In general, the accelerator 2504 may be structurally configured to accelerate a fluid stream through the extractor 2502, past the extractor 2502, or created by the extractor 2502, thereby creating an accelerated fluid stream (e.g., the second fluid flow 2510) in the device 2500. The accelerator 2504 may thus condense a fluid stream directed toward the extractor 2502, through the extractor 2502, or in a flow path downstream of the extractor 2502.

The device 2500 may be configured to prevent or limit disturbances in the fluid flow created by the extractor 2502 within the accelerator 2504. These disturbances may include blockage as described herein. The disturbances (e.g., blockage) may be caused by an extractor 2502 featuring rotors (e.g., rotor blades or the like), where the rotors create a low velocity, high pressure region that extends out from the center of a hub of the rotor to a surface of the accelerator 2504. In this manner, the edges of the fluid flow disposed at or near the surfaces of the accelerator 2504 may form wakes, e.g., caused by high mass flow in a confined channel of the accelerator 2504. These wakes created towards the outside/edges of the accelerator 2504 may cause blockage. In some extractors/accelerators, the blockage can be so significant that it almost defeats the purpose of the accelerator 2504. It may thus be desirous to include an extractor feature 2506 that reduces the mass flow to the edges of the device 2500 near the surfaces of the accelerator 2504.

The extractor feature 2506 may be structurally configured to minimize blockage of the accelerated fluid stream (e.g., mitigate non-power blockage in the fluid stream). The extractor feature 2506 may be present on, be part of, or otherwise be in mechanical or fluid communication or cooperation with, one or more of the extractor 2502 and the accelerator 2504. In an aspect, the extractor feature 2506 is disposed on the accelerator 2504 (e.g., the extractor feature 2506 is basically a feature of the accelerator 2504). In another aspect, the extractor feature 2506 is disposed on the extractor 2502. The extractor feature 2506 may be structurally configured to minimize individual extraction plane flow effects by reducing individual plane solidity, e.g., thereby minimizing blockage as described herein.

The extractor feature 2506 may include one or more of a linear cascade, an oscillating foil, and an axial extractor.

In an aspect, the extractor feature 2506 includes a linear cascade (e.g., an n-stage linear cascade). The linear cascade, for example, may be the same or similar to any of those as described herein, e.g., with reference to one or more of FIGS. 16, 19 and 20. For example, in an aspect, the extractor feature 2506 includes a linear cascade that includes two or more co-planar blades and a stage solidity of less than about 20%.

In an aspect, the extractor feature 2506 includes an oscillating foil (e.g., an n-stage oscillating foil). The oscillating foil, for example, may be the same or similar to any of those as described herein, e.g., with reference to one or more of FIGS. 1-8. For example, in an aspect, the extractor feature 2506 includes an oscillating foil that includes two or more co-planar foils and a stage solidity of less than about 20%.

In an aspect, the extractor feature 2506 includes an axial extractor (e.g., an n-stage axial extractor). The axial extractor, for example, may be the same or similar to any of those as described herein, e.g., with reference to FIG. 11. For example, in an aspect, the extractor feature 2506 includes an axial extractor that includes two or more co-planar collapsible foils and a stage solidity of less than 20%. The axial extractor may thus be a feature of the extractor 2502, or may replace or supplement the extractor 2502 of the device 2500.

The extractor feature 2506 may be structurally configured to minimize blockage by minimizing flow effects engendered by power extraction. The extractor feature 2506 may also or instead extract power from a mono or bidirectional radial motion. In an aspect, the mono or bidirectional radial motion includes a linear cascade. The extractor feature 2506 may extract power from an axial motion. In an aspect, power from the axial motion is extracted by one or more of a piston and collapsible kite configuration or an electrostatic system. Implementations may also or instead include an extractor feature 2506 that extracts power from a combination of axial and radial motion. In an aspect, the combination of axial and radial motion is caused by one or more of an oscillating foil or an unsteady aerodynamics configuration.

The extractor feature 2506 may be structurally configured to extract power from a volume by utilizing multiple extraction planes. One skilled in the art will recognize that an example of an extraction plane is shown by the line that also represents the extractor 2502 in the figure. The extractor feature 2506 may also or instead be structurally configured to minimize flow effects by minimizing a size of one or more extractor elements relative to boundaries of the accelerator 2504 and other extraction planes. The flow effects may include wakes.

In other words, the smaller the element (e.g., the extractor feature 2506 or components thereof), the more localized the effect the element has on the flow. In this manner, an improved device 2500 may include multiple small elements that create partitioned wakes rather than large wakes that a single large element would create. For example, for 1 m² of surface area, it may be advantageous to have ten 0.1 m² surface areas rather than a single 1 m² area.

The extractor feature 2506 may be structurally configured to reduce individual plane solidity to minimize individual extraction plane flow effects. The extractor feature 2506 may also or instead be structurally configured to limit flow effects to an outside of a swept area by increasing a number and reducing a size of one or more extractor elements. The extractor feature 2506 may also or instead be structurally configured to counterbalance effects to an outside of a swept area in at least one of a two-dimensional or three-dimensional anhedral configuration thereby reducing one or more of a tip leakage or a tip vortex expansion angle. In other words, typically on a straight blade rotor, the fluid may “leak” up the blade spinning of a tip vortex. Tilting the blade forward (such as in an anhedral) may reduce the percentage of fluid that leaks up the blade as the tilt counterbalances the centripetal force.

The extractor feature 2506 may also or instead be structurally configured to minimize blockage between extractor elements by changing a geometry of an extractor blade row (e.g., the space between the blades) from a nozzle to one or more of a tube or diffuser configuration that utilizes an axial offset in one or more of a spiral or angled configuration.

The extractor feature 2506 may also or instead include a brim on the accelerator 2504, drill throughs, double annular shells, or the like.

FIG. 26 shows a device for fluid power generation. Specifically, this figure shows a device 2600 having a plurality of accelerator-extractor pairs in the form of turbines 2602 disposed in channels 2604.

The above systems, devices, methods, processes, and the like may be realized in hardware, software, or any combination of these suitable for a particular application. The hardware may include a general-purpose computer and/or dedicated computing device. This includes realization in one or more microprocessors, microcontrollers, embedded microcontrollers, programmable digital signal processors or other programmable devices or processing circuitry, along with internal and/or external memory. This may also, or instead, include one or more application specific integrated circuits, programmable gate arrays, programmable array logic components, or any other device or devices that may be configured to process electronic signals. It will further be appreciated that a realization of the processes or devices described above may include computer-executable code created using a structured programming language such as C, an object oriented programming language such as C++, or any other high-level or low-level programming language (including assembly languages, hardware description languages, and database programming languages and technologies) that may be stored, compiled or interpreted to run on one of the above devices, as well as heterogeneous combinations of processors, processor architectures, or combinations of different hardware and software. In another aspect, the methods may be embodied in systems that perform the steps thereof, and may be distributed across devices in a number of ways. At the same time, processing may be distributed across devices such as the various systems described above, or all of the functionality may be integrated into a dedicated, standalone device or other hardware. In another aspect, means for performing the steps associated with the processes described above may include any of the hardware and/or software described above. All such permutations and combinations are intended to fall within the scope of the present disclosure.

Embodiments disclosed herein may include computer program products comprising computer-executable code or computer-usable code that, when executing on one or more computing devices, performs any and/or all of the steps thereof. The code may be stored in a non-transitory fashion in a computer memory, which may be a memory from which the program executes (such as random access memory associated with a processor), or a storage device such as a disk drive, flash memory or any other optical, electromagnetic, magnetic, infrared or other device or combination of devices. In another aspect, any of the systems and methods described above may be embodied in any suitable transmission or propagation medium carrying computer-executable code and/or any inputs or outputs from same.

It will be appreciated that the devices, systems, and methods described above are set forth by way of example and not of limitation. Absent an explicit indication to the contrary, the disclosed steps may be modified, supplemented, omitted, and/or re-ordered without departing from the scope of this disclosure. Numerous variations, additions, omissions, and other modifications will be apparent to one of ordinary skill in the art. In addition, the order or presentation of method steps in the description and drawings above is not intended to require this order of performing the recited steps unless a particular order is expressly required or otherwise clear from the context.

The method steps of the implementations described herein are intended to include any suitable method of causing such method steps to be performed, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. So for example performing the step of X includes any suitable method for causing another party such as a remote user, a remote processing resource (e.g., a server or cloud computer) or a machine to perform the step of X. Similarly, performing steps X, Y and Z may include any method of directing or controlling any combination of such other individuals or resources to perform steps X, Y and Z to obtain the benefit of such steps. Thus method steps of the implementations described herein are intended to include any suitable method of causing one or more other parties or entities to perform the steps, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. Such parties or entities need not be under the direction or control of any other party or entity, and need not be located within a particular jurisdiction.

It should further be appreciated that the methods above are provided by way of example. Absent an explicit indication to the contrary, the disclosed steps may be modified, supplemented, omitted, and/or re-ordered without departing from the scope of this disclosure.

It will be appreciated that the methods and systems described above are set forth by way of example and not of limitation. Numerous variations, additions, omissions, and other modifications will be apparent to one of ordinary skill in the art. In addition, the order or presentation of method steps in the description and drawings above is not intended to require this order of performing the recited steps unless a particular order is expressly required or otherwise clear from the context. Thus, while particular embodiments have been shown and described, it will be apparent to those skilled in the art that various changes and modifications in form and details may be made therein without departing from the spirit and scope of this disclosure and are intended to form a part of the invention as defined by the following claims, which are to be interpreted in the broadest sense allowable by law. 

What is claimed is:
 1. A device comprising: an extractor structurally configured to extract energy from a fluid flow; an accelerator structurally configured to accelerate a fluid stream through the extractor thereby creating an accelerated fluid stream; and an extractor feature structurally configured to minimize blockage of the accelerated fluid stream, the extractor feature including one or more of a linear cascade, an oscillating foil, and an axial extractor.
 2. The device of claim 1 wherein the extractor feature is structurally configured to minimize individual extraction plane flow effects by reducing individual plane solidity.
 3. The device of claim 2 wherein the extractor feature includes the linear cascade, the linear cascade including two or more co-planar blades and a stage solidity of less than 20%.
 4. The device of claim 2 wherein the extractor feature includes the oscillating foil, the oscillating foil including two or more co-planar foils and a stage solidity of less than 20%.
 5. The device of claim 2 wherein the extractor feature includes the axial extractor, the axial extractor including two or more co-planar collapsible foils and a stage solidity of less than 20%.
 6. The device of claim 1 wherein the extractor feature is structurally configured to minimize blockage by minimizing flow effects engendered by power extraction.
 7. The device of claim 6 wherein the extractor feature extracts power from a mono or bidirectional radial motion.
 8. The device of claim 7 wherein the mono or bidirectional radial motion includes a linear cascade.
 9. The device of claim 6 wherein the extractor feature extracts power from an axial motion.
 10. The device of claim 9 wherein power from the axial motion is extracted by one or more of a piston and collapsible kite configuration or an electrostatic system.
 11. The device of claim 6 wherein the extractor feature extracts power from a combination of axial and radial motion.
 12. The device of claim 11 wherein the combination of axial and radial motion is caused by one or more of an oscillating foil or an unsteady aerodynamics configuration.
 13. The device of claim 1 wherein the extractor feature is structurally configured to extract power from a volume by utilizing multiple extraction planes.
 14. The device of claim 1 wherein the extractor feature is structurally configured to minimize flow effects by minimizing a size of one or more extractor elements relative to boundaries of the accelerator and other extraction planes.
 15. The device of claim 14 wherein the flow effects include wakes.
 16. The device of claim 1 wherein the extractor feature is structurally configured to reduce individual plane solidity to minimize individual extraction plane flow effects.
 17. The device of claim 1 wherein the extractor feature is structurally configured to limit flow effects to an outside of a swept area by increasing a number and reducing a size of one or more extractor elements.
 18. The device of claim 1 wherein the extractor feature is structurally configured to counterbalance effects to an outside of a swept area in at least one of a two-dimensional or three-dimensional anhedral configuration thereby reducing one or more of a tip leakage or a tip vortex expansion angle.
 19. The device of claim 1 wherein the extractor feature is structurally configured to minimize blockage between extractor elements by changing a geometry of an extractor blade row from a nozzle to one or more of a tube or diffuser configuration that utilizes an axial offset in one or more of a spiral or angled configuration. 